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It is found that the duration of life depends directly upon the humidity of the air, 
being greatest at one vapor pressure and least at another; but these points do not 
coincide for all kinds of pollen. There are only a few species which live longest 
in very moist air (90-60 per cent.), and only one that lives the same length of time 
in moist as in dry air; but there are many species which live longest in very dry 
air (30-0 per cent.). (A priori, it would seem that all pollen should remain alive 
longest in absolutely dry air, and one wonders whether the differences found by 
Pfundt are not due to some other factors, for whose operation there is ample 
room in the handling of the material, and particularly in the artificial germina- 
tion tests on which the conclusions are based.) In nature the duration of life 
is very variable because of the variations in the moisture of the air. The influence 
of a single change from moist to dry is not very evident, but repeated changes 
shorten life, and the drying of wet pollen leads quickly to death, the sooner the 
longer it was wet. Ecological adaptations are not clear; the pollen of early 
spring and late autumn flowers, however, is generally long-lived, shows little 
sensitiveness to moisture, and germinates at minimum temperatures, even below 
4-5°. Whereas freshly gathered pollen may germinate in dilute or in concen- 
trated solutions indifferently, that which is about to die produces tubes only in 
the most favorable concentration. — C. R. B. 

Morphology of Salvinia. — Arnoldi 21 has published the results of a study of 
Salvinia natans. The paper is divided into three parts: (1) the germination of the 
microspore and the development of the male gametophyte; (2) the germination of 
the megaspore and the development of the female gametophyte, fertilization, and 
embryo formation; (3) a series of experiments on the female gametophyte. In 
the first part little is added to Belajeff's account except such cytological details 
as the size of nuclei and chromosomes, the number of chromosomes (4), and the 
spermatogenesis. The early stages of the female gametophyte were followed more 
closely than by previous authors. It is found to be composed of a coenocytic 
portion contained within the old spore wall, and an exposed chlorophyll-bearing 
tissue, one side of which bears archegonia. In the mature archegonium, the axial 
row consists of the egg, the ventral canal cell, and a broad wedge-shaped neck canal 
cell which is binucleate. In the third part of the paper the following facts are 
recorded: (1) an unsuccessful attempt to produce apogamous embryos: (2) the 
appearance of the archegonia in the upper or lighter side of the prothallium is 
not a response to light; (3) the development of the winglike appendages, charac- 
teristic of the female gametophyte of Salvinia, occur only when fertilization and 
embryo formation precede it; (4) the food material used by the developing 
embryos is not made by the chlorophyllose tissue of the gametophyte, but is that 
which was stored in the megaspore; (5) spores sown on damp clay germinated 
and produced good prothallia with normal archegonia and embryos. — Wanda M. 

21 Arnoldi, W., Beitrage zur Morphologie der Keimung von Salvinia na/ans. 
Flora 100:121-139. figs. 47. 1909.